Hydraulic pressure-multipliers



Oct. 9, 1962 G. H. ALPING 3,057,163

HYDRAULIC PRESSURE-MULTIPLIERS Filed March 24, 1961 INVENTOR.

GUSTAV HENRY ALPI NG A TTORNEY United States Patent O 3,057,163 HYDRAULIC PRESSURE-MULTIPLIERS Gustav Henry Alping, Enisoping, Sweden, assignor to Aktiehoiaget Bahco, Stockholm, Sweden, a corporation of Sweden Filed Mar. 24, 1961, Ser. No. 98,113 6 Claims. (Cl. Gil-54.6)

The present invention relates to a hydraulic pressuremultiplier having two stages, a low-pressure stage and a high-pressure stage, of the kind comprising a low-pressure piston movable in a cylinder and provided with a central axial bore serving as a cylinder fo-r a reciprocating high-pressure piston. The invention is especially adapted to be used for -actuating the 4work-fastening jaws in machine tools and the like.

The object of this invention is to provide a two-stage hydraulic pressure-multiplier wherein the transition from one stage to the other takes place automatically at a predetermined pressure level.

This is achieved according to the present invention in that the low-pressure piston is actuated by a sleeve-like member provided with outer threads cooperating with inner threads in the rear end of the cylinder and with inner threads in a handle, to which the high-pressure piston is connected, said handle being provided with a locking device which normally connects the handle tothe sleeve-like member, but when the pressure produced by the low-pressure piston has reached a predetermined value, releases the handle so that this can be screwed onto the sleeve-like member together with the high-pressure piston.

The invention will be further described in connection with the embodiment shown on the attached drawing, which shows a hydraulic pressure-multiplier in axial section.

In the embodiment illustrated, the hydraulic pressuremultiplier comprises a main cylinder 1 in which a lowpressure piston 2 is movable between which and the end wall of the cylinder the working chamber 3 of the pressuremultiplier is formed. This working chamber is by means of a hose 4 o-r the like connected to for instance a fa-stening device of a type known per se in machine tools, (not shown). A sleeve-like member 7 provided with outer threads 6 cooperates with inner threads 5 at the rear end of the cylinder 1. A hand-wheel consisting of a hub 8 and arms 9 projecting therefrom is screwed onto the rear end of the sleeve-like member 7. The piston 2 is provided with an axial bore 10 forming a cylinder for a high-pressure piston 11 cooperating therewith. This high-pressure piston 11 is with its rear end connected to the hub 8 of the hand-wheel so as to be rotatable but not axially movable with respect thereto. In one of the arms 9 of the hand-wheel a spring-loaded rod 12 is provided which acts on a locking ball 13 cooperating with an aperture in the thread at the rear end of the sleeve-like member 7. The spring pressure acting on the ball 13 is suitably adjustable. The front end of the sleeve-like member 7 bears on an annular abutment edge 14 on the low-pressure piston 2 and a helical spring 17 is provided between an abutment edge 15 at the forward end of the member 7 and an abutment ring 16 at the rear end of the low-pressure piston 2. In order to limit the rearward movement of the low-pressure piston 2 a stop-screw 18 is screwed through the cylinder wall and projects into an annular recess 19 in the low-pressure piston. The rearward movement of the hand-wheel 8, 9 is determined by the locking device 12, 13 and by a sleeve member 20 iixed to the han-d-wheel and provided with a flange 21 which in the rear position cooperates with an annular abutment edge 22 at the rear end of the cylinder.

3,057,163 Patented Oct. 9, 1962 position shown on the drawing where the locking ball 13 is received in the recess provided therefor in the thread 6, in such a direction that the sleeve-like member 7 is screwed into the cylinder 1 and thus moves the lowpressure piston 2 inwards. When thereby the pressure in the working chamber 3 and in the hose 4 has reached a certain value the resistance becomes so high that the locking ball 13 moves out of the recess against the action of the spring loaded rod 12, so that on continued turning of the handwheel this is screwed forwards on the sleeve-like member 7. This result-s in also the highpressure piston 11 moving forward and carrying out its working stroke, the length of which is determined by the pressure desired in the hose 4.

When later on the pressure shall be permitted to decrease, i.e. when the fastening device shall be loosened lthe hand-wheel is turned in the opposite direction, whereby firstly the hand-wheel returns to its rear end position together with the high-pressure piston 11 where the locking ball 13 enters into the recess in the thread 6.

On continued turning of the hand-wheel the sleevelike member 7,is screwed out of the cylinder so that the lowpressure piston 2 is permitted to move rearwards in the working chamber. The rearward movement of the member 7 is limited by the flange on the sleeve member 20 cooperating with the abutment edge 22.

lf for some reason the low-pressure piston 2 has got stuck in its forward position the hand-wheel can be turned in spite of this to such an extent in the rearward direction that the flange 21 will come into Contact with the abutment edge 22. This is possible on account of the fact that the sleeve-like member 7 is allowed to move in the axial direction relatively to the piston 2 against the action of the spring 17 but in this case the piston is turned together with the sleeve-like member by means of a pin 24 projecting into a groove 23 in the rear end of the piston. Thus the extra spring load as well as the turning of the piston 2 will assist in loosening the same. If furthermore the fastening device gets stuck this device is also of a very great importance as the piston already at a relatively small vacuum can stop in spite of continued turning of the hand-wheel, and this effectively prevents the occurrence of too great a vacuum which could result in air being sucked into the system.

The invention is not limited to the now shown and described embodiment but it can be changed in various ways within the scope of the invention.

I claim:

l. In a hydraulic pressure-multiplier having a low pressure stage and a high pressure stage of the type including a low pressure piston movable in an outer cylinder and provided with a central axial bore serving as an inner cylinder for a reciprocating high pressure piston, the improvement comprising a sleeve-like member provided with outer threads cooperating with inner threads in the rear end of said outer cylinder to move the low pressure piston, a handle having inner threads meshing with the threads of said member and connected with said high pressure piston, a locking device on said handle which normally connects the handle to the sleeve-like member but when the pressure produced by the low pressure pisto-n has reached a predetermined value releases the handle to screw onto the sleeve-like member and move the high pressure piston with respect to the member and inner cylinder.

2. In a hydraulic pressure-multiplier the improvement according to claim 1 wherein the locking device comF prises a spring loaded locking ball cooperating with a recess in the sleeve-like member.

3. In a hydraulic pressure-multiplier the improvemen-t according to claim 2 wherein the spring load acting on the locking -ball is adjustable.

4. In a hydraulic pressure-multiplier the improvement according to claim 1 wherein the handle is provided with a sleeve projecting towards and surrounding the outer cylinder, said sleeve being provided with an annular flange which in the rear'position of the handle cooperates with an abutment on the cylinder.

5. In a hydraulic pressure-multiplier the improvement according .to claim 1 wherein the sleeve-like member is rotatably connected to the low pressure pis-ton -by a pin and slot connection rendering the low pressure piston movable axially relatively to the member only to a limited extent.

6. In a hydraulic pressure-multiplier the improvement according to claim 1 wherein the outer cylinder is provided with an abutment which limits the rearward movement of the low pressure piston.

References Cited in the tile of this patent UNITED STATES PATENTS 2,185,264 Mistral Jan. 2, 1940 2,803,157 Seltter Aug. 20, 1957 FOREIGN PATENTS 231,829 Switzerland July 17, 1944 

